The invention relates to a serial bus communication system.
A serial bus typically distorts signals that propagate across the bus. For example, the serial bus may include conductive signal lines (copper lines, for example) to communicate digital signals from a transmitter to a receiver. The signal lines typically introduce a dispersive transfer function to the fourier components of the digital signals. As a result of this dispersive transfer function, data communication may not exceed a maximum data communication rate (typically expressed in terms of Megabits/sec Kilometer). Otherwise, if communication of the data above the maximum data communication rate is attempted, the lines may attenuate the magnitudes of the digital signals and shift the phases of the digital signals to fully close the receiver""s xe2x80x9ceye opening,xe2x80x9d an opening established by the time that is available at the receiver to re-clock the data and the voltage difference at the receiver between the logic one and the logic zero voltage levels.
Several techniques may be used to compensate for the distortion that is introduced by the serial bus. For example, a technique called adaptive equalization may be used. With adaptive equalization, the distorted digital signals are received from the lines of the serial bus and are routed through analog filters that are coupled between the lines of the serial bus and the receiver. These analog filters apply gain/loss factors and phase shifts to the distorted digital signals for purposes of removing the distortion. However, a potential problem with this approach is the cost and complexity that are associated with analog filtering.
Another technique to compensate for the distortion that is introduced by the serial bus is pre-compensation, a technique in which a distortion function is applied to each digital signal before the digital signal is communicated to the signal line of the serial bus. Due to this compensation, the digital signals should appear relatively undistorted near the receiver. However, in the past, an estimation of the distortion that is introduced by a particular line of the serial bus was used to develop pre-compensation filters to reduce the distortion. Unfortunately, this estimation may be imprecise, and to the extent that the estimation is incorrect, the digital signal may appear substantially distorted at the receiver.
Thus, there is a continuing need for an arrangement to more precisely compensate for distortion that is introduced by a serial bus.